Question
I have a 5 head Weinig moulder. I am wondering how to achieve a little better finish on my product after running mouldings. I am using a good high grade of high speed steel for the knives in the profiles I run. I run all lumber through mostly at 15/16" hit and miss.
What I run into is after I have a set re-sharpened, I will get a good run on say 1500-2500'. Then the next knife I have re-sharpened it never fails that I start seeing some light lines in the mouldings. Now I will take samples and put stain on them and usually they don't pull out, are these normal machining lines? I feel I need to sand these lines out by hand roughly, and most of the time it's only in the flat areas of a profile. I’m trying to figure out how to be more consistent when running mouldings. I have seen carbide do this also.
Forum Responses
(Architectural Woodworking Forum)
From contributor G:
If you are staining it you should be sanding it. Maybe us a Superbrush.
The first thing for us is we never put straight 15/16 lumber into the moulder. We always surface it to remove the dirt and grit from the mills and we also end trim the leading edge going into the moulder. This helps the life of the knives and allows us to run longer. This is particularly true for abrasive planed lumber.
The second part of the equation is good knife grinding skills. This means watching balance, backgrinds, pocket angles, knife projection, head distortion, so on and so on. One tip is you may try using a secondary bevel so touching up on the grinder is easier and more precise.
The last part is we sand all our flat stock e2e, or any moulding that has a wide flat surface using the overhead sander. It requires a little planning so as you generate new profiles leaving the detailed section lower than the flat. We personally don't sand the detail portion of any moulding but we don't do any stain work either. That of course doesn't mean specialty products, radius, handrails, etc. The next thing you could look into is a profile sander.
If the lines run lengthwise it is most likely either a knife defect or there is something imbedded in the top pressure shoe. Check the knives before you put them in the head. Is there a wire edge still on them from grinding? (You can knock it off with a piece of hardwood drug along the edge). Was the last grind done with a course wheel at too slow of rpm? Was the last grind forced too fast, not enough coolant flow? Was the secondary bevel not enough (skips) or too much? I'll assume you are not running a jointed molder.
If all else fails start from scratch. Go back to the tooling bench, remove the knives and clean the head slots and knife corrugations. Put the knives in and torque bolts progressively, go to the profile grinder and make sure your template is supper smooth and the flat parallel to the axis. Do a careful primary grind with lots of coolant then shift the wheel speed to high and do a very slight secondary grind at the correct angle. Check for the wire edge and get rid of it. Go over your molder setup process very carefully. All of this isn't of much value if you run dirty boards (one of the values of a 6 head).
One of the things we do for longer runs is use double back carbides in alternative slots for the flats. You can grind them on your profile grinder with a diamond wheel even if your grinder doesn't have axial adjustment. It may take some fiddling to get the levels of the steel and carbide knives to line up well. The double back knives have very fine corrugations which helps. Feed speed for single knife cutting and nice quality: 30 to 35'/min.
What confuses me is you’re saying you get about 1500-2500' good feet on a new set of knives but when they get re-sharpened you start getting lines. You should get the exact same footage if the guy sharpening the knives is the guy making the knives. I don’t know, maybe I’m missing something.
I rip all my blanks for the job. I set the moulder up and run some test pieces. Now it could happen with new knives or even just re-shaprpened knives that I see these light lines going with the grain. They look like very small nicks in the knives. Now I have seen them in products where the manufacturer is using carbide on high speed machines.
Again, if I hold up in light, they are there but only someone trained will see them. Now other times they can be really visible and for sure have to hand sand the mouldings before I send to customer. Now this can happen within the first 50' or fewer or it can happen after 1000 or 1500'.
As I stated before, am I being too picky if I hand sand the light line even though when I take the sample and put stain and varnish on it it is not visible? My competitors are beating me up on price but they also are running mouldings that you clearly see these lines bad once stained. I’m looking for a cost effective way to do less sanding and running a better moulding. I run everything around 27fpm. I do see on some profiles that have a few bumps due to the hold down but otherwise I get great comments all the time. Just looking for insight if a moulding sander really works or not. My next purchase when cash is available is a knife grinder.
A little warning though, anything that can fix and edge can also damage it. It can take a good six months of practice for someone to learn to hone with consistent results but is a very useful skill. I’d suggest practicing on dull blades at the end of a run when your timeline is not crucial.
I will reiterate, it takes one piece of wood with a little dirt and grit on it to make your knives do just what you’re describing. Clean wood is paramount, standard hit and miss mill lumber can be sitting around for a long time out in a dirty dusty yards and that is pure abrasive. If you don't have a planer, have your supplier send it to someone who does and have them surface it for you. Then don't do what I caught one of my guys doing, use a piece of sticker material for a setup stick!
